The time has come I just replaced the 6v6's with JJ's and noticed 2 of the 12AX7As are gone too any recomendations on what is best to get. I had a choice between tunsol and JJs the guy at the store reccomended jjs ??? they didn't have groove tubes 6v6 ??

Thanks Mike they sound nice I looked a little closer it looks like each pre-amp has 2 12ax7a and 1 12at7 It is actually the 12at7 that are blown I am thinking I just have to replace one of these any thoughts on this should I be using tubes in the pre-amp I am not using ???

If I am following you, and I'm a little fuzzy on pain meds since a wisdom tooth came out a couple days ago, my answer is to just replace the bad tube, no need to replace them all.

gdrfk1990 wrote:Thanks Mike they sound nice I looked a little closer it looks like each pre-amp has 2 12ax7a and 1 12at7 It is actually the 12at7 that are blown I am thinking I just have to replace one of these any thoughts on this should I be using tubes in the pre-amp I am not using ???

I swapped tubes in a Twin once without rebiasing and blew the transformer. That was an expensive repair bill. Your mileage may vary, but I'd personally be sure to have it biased or at least make sure the tubes match the bias now. I don't own a DR, just a Twin, but they're similar beasts. My advice is to make a phone call to an amp tech in your area before you have an accident.

I always buy my power tubes in sets of 4 matched tubes. That way, if you blow one at a gig, you can quickly swap in a replacement without rebiasing. And if you don't blow any, when the first two are spent, simply replace them with the remaining pair. Also, if possible, ask the supplier to give you the bias numbers as, assuming you like how they sound, you can then order similar new tubes, again without a need to rebias. Indeed, some tube suppliers pre-match their tubes this way and you simply order by number, e.g., MESA.